Stopping Conditional Formatting until subject cells have been populated

Hi
I am setting up a sheet that will change the colour of a particular row when a task is completed within a certain time frame which is also sourced from the same row but another cell. Basically I have a start time, end time and acceptable timeframe. The row will change green if the difference between the start time and the end time is within the acceptable timeframe and red if it is not.

My problem is that as soon as I input the start time the row turns green. I want it to be that the row remains 'no colour' until the three cells that populate the conditions are filled.

Current conditions are
condition 1 formula is=$A3>($C3-$B3) then fill colour green
condition 2 formula is=$A3<($C3-$B3) then fill colour red
condition 3 formula is=ISBLANK then no fill colour

where A3 is acceptable timeframe, C3 is endtime, B3 is startime

As soon as I enter a time into B3 then the row turns green when I would like no change in colour until all cells have information in them.

Any help would be appreciated.

Thanks.

count the cells that have been filled in:

=counta($A3:$C3)=3

condition 1 formula is=and(counta($A3:$C3)=3,$A3>($C3-$B3)) then fill colour green
etc